Process for flameproofing cellulosic material



United States Patent 3,403,044 PROCESS FOR FLAMEPROOFING CELLULOSIC MATERIAL Leon H. Chance, New Orleans, and George L. Drake, Jr., and Wilson A. Reeves, Metairie, La., assignors to the United States of America as represented by the Secretary of Agriculture N0 Drawing. Filed Mar. 26, 1965, Ser. No. 443,113 6 Claims. (Cl. 11762.2)

ABSTRACT OF THE DISCLOSURE Flame retardant cotton fabric, durable to laundering, was prepared by treatment with aqueous precondensates of tetrakis(hydroxymethyl)phosphonium chloride (THPC) and phosphoroxytriamide (PTA) or dimethylamidophosphoroxydiamide (DPDA) in mole ratios of THPC to PTA or DPDA of 0.5:1 to 6:1.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the 'United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention, together with the invention disclosed in Ser. No. 443,108 filed of even date, is a further improvement in or modification of the invention claimed in U.S. Patents No. 2,772,188, No. 2,983,623, and No. 3,276,897. More particularly, this invention relates to the treatment of cellulosic materials with a partially polymerized water soluble product containing a further polymerizable polymer which contains phosphorus and nitrogen, and which is insolubilized within the cellulosic material with ammonia, or with heat, thereby producing a flame-retardant cellulosic material have improved strength retention after chlorine bleaching and scorching.

U.S. Patent No. 2,772,188 defines the nature of the further-polymerizable compounds as methylol-phosphorus polymers in one of the Water soluble stages when applied to the cellulosic materials. The invention then describes a process to further polymerize methylol-phosphoruspolymers without the use of heat. This further polymerization is accomplished by using ammonia, in the form of gaseous ammonia, ammonium hydroxide, a solution of ammonia in an inert solvent, or as ammonia released in situ by the reaction of a compound capable of releasing ammonia, e.g., an ammonium salt of a weak acid, such as ammonium acetate.

U.S. Patent 2,983,623 claims an improved method of insolubilizing the further-polymerizable methylol-phosphorus polymeric materials 'by treating with gaseous ammonia first and aqueous ammonia afterwards. The process described in Patent 2,983,623 is briefly: impregnation of a cellulosic material with an aqueous solution or dispersion of a further-polymerizable methylol-phosphorus polymeric material; drying the cellulosic material; treating the cellulosic material in ammonia gas; treating the cellulosic material in aqueous ammonia; washing, rinsing, and drying the cellulosic material.

Whereas any of the further-polymerizable methylolphosphorus polymeric materials referred to in Patent 2,772,188 are satisfactory for the processes of Patent ice 2,983,623, a particularly suitable polymeric material is claimed to be the reaction product of tetrakis(hydroxymethyl) phosphonium chloride (THPC) and urea. Scoured and bleached cotton fabric treated by this process was flame resistant, passing the standard vertical flame test (Fed. Spec. CCC-T-191b). The treated fabric was fairly stiff, and when given a chlorine bleach turned yellow. Furthermore, after chlorine bleaching and scorching, the fabric retained only 25-30% strength.

Particularly suitable precondensates referred to in U.S. Patent No. 3,276,897 are claimed to be the reaction products of (THPC) and tris(carbamoylethyl)amine or ethyl carbamate. Cellulosic materials which contain these polymers are claimed to show virtually no discoloration and very little strength loss after chlorine bleaching and scorching.

It is the object of this invention to provide a method of preparation of new preoondensates and a process for the application of the precondensate to impart improved flame resistance to cellulosic materials.

Another object of this invention is to provide white cellulosic materials which retain essentially all of their breaking strength after chlorine bleaching and scorching.

Still another object of this invention is to provide a method of producing cellulosic materials which retain their flame-retarding properties after frequent washings.

These and other objects of this invention will be apparent to those skilled in the art of making flame retardant cellulosic materials.

Methylol-phosphorus polymeric materials are produced by reacting at least one compound of the group tetrakis- (hydroxyrnethyl)phosphonium chloride, tris(hydroxymethyl)phosphine oxide, and phosphorus-linked methylolgroup-containing derivatives thereof, with compounds containing a plurality of groups which yield condensation products with a phosphorus-linked methylol group.

The process of this invention is particularly useful in the insolubilization of nitrogen methylol-phosphorus poly- ,mers with ammonia. Preferred nitrogen methylol-phosphorus polymers are produced by reacting at least one phosphorus compound of THPC and/or THPO with a compound from the group consisting of phosphoroxytriamide and dimethylamidophosphoroxydiamide.

In accordance with this invention, any cellulosic material, such as cotton, rayon, paper, jute, ramie, and the like, may be treated, but the invention is particularly ellifective when applied to the treatment of cellulosic text' es.

In preparing the further polymerizable nitrogen methylol-phosphorus polymers, the aforementioned compounds are mixed with water and partially polymerized to form a precondensate. This may be at any temperature from room temperature to the reflux temperature. When the partial polymerization takes place at the reflux temperature, one-half hour is usually adequate. A particularly suitable polymeric material is the reaction product of tetrakis(hydroxymethyl)phosphonium chloride (THPC) and phosphoroxytriamide (PTA), in mole ratios of THPCzPT-A 0130.5:1 to 6:1.

The cellulosic material is impregnated with the aqueous solution of the precondensate, preferably by padding, although other impregnating techniques may be used; the

of its warp breaking excess solution is removed by passing the cellulosic material through squeeze rolls, centrifuging, or other methods. The impregnated cellulosic material is then dried. The drying temperature can vary about from room temperature to 145 C., although 80-90" C. is preferred; the drying time varies from several hours (at room temperature) to a few minutes at the higher temperatures. For example, drying of the cellulosic material can be effected in a conventional forced hot air oven for five minutes at 80 C.

Insolubilization of the precondensate with ammonia is accomplished in two steps. First, the dried cellulosic material containing the further polymerizable methylolphosphorus polymer is exposed to gaseous ammonia and then to ammonium hydroxide. The gaseous ammonia may be applied at temperatures of about from 25 C. to 100 C.; the aqueous ammonia may be from about 10-29% ammonium hydroxide.

In cases where insolubilization with ammonia is not used, the material is cured at temperatures about from 80 C. to 155 C. The treated cellulosic materials are then washed and dried.

Cellulosic materials treated in accordance with this invention have improved flame-retardant properties which are retained after repeated launderings. When cellulosic materials treated in accordance with this invention are given a chlorine bleach and subsequently scorched, the warp breaking strength retention is more than 90%.

The following examples illustrate the methods of carrying out the invention but the invention is not restricted to these examples. Treated fabrics were tested by the standard methods of the American Society for Testing tMaterials, Philadelphia, Pa., Committee D-13. Breaking strength was determined by the one-inch strip method, ASTM designation, D39-59; tearing strength by the Elmendorf method, ASTM designation, D1295-60T; damage by chlorine, by ASA Method, No. l, 14.126-1961; and flame resistance by the standard vertical method, Fed. Spec. CCC-T-l9lb. The percentages and parts are by weight.

Example 1 Solutions were prepared by dissolving tetrakis(hydroxymethyl) phosphonium chloride (THPC) and phosphoroxytriamide (PTA) in water as indicated in Table I.

TABLE I Solution Parts Parts Parts Mole ratio pH of No. of THPC of PTA of H THPC :ITA solution Solution No. 1 gelled within 2-3 hours, so it was necessary to apply it to cotton fabric before gelling, preferably within one hour after mixing. Solution No. 7 gelled within 20-25 minutes after mixing. It also had the unusual property of reliquifying after about 5-6 hours, and regelling within several days. Best results with these two solutions were obtained by applying to fabric immediately after preparation. All of the other solutions 'were stable for extended periods of time without gelling.

The solutions in Table I were padded onto OD sateen and each sample of fabric dried for five minutes at 85 C. The samples treated with solutions 3, 4, 5, and 6 were then exposed to NH gas for three minutes at room temperature (about C.) and then immersed in 10% NH OH for three minutes at room temperature. Samples of fabric treated with Solutions 1 and 2 were not exposed to NI-I gas or to NH OH solution, but were allowed to stand at room temperature (26 C.) for 24 hours. The sample of fabric treated with solution No. 7 was not ex- TABLE II Solution used, No.

Add-on,

Before laundering percent After ten laundering cycles 1? content, N content, P content, N content, percent percent percent percent All samples in Table II had good flame resistance except samples treated with Solutions 2 and 7. This was due to the low add-on. Most samples retained considerable phosphorus and nitrogen after ten home laundering cycles. The sample treated with solution No. 7 retained all of its phosphorus after ten home laundering cycles.

Example 2 A solution was prepared containing 2388 parts of THPC, 2.38 parts of PTA, and 53.30 parts of water. The pH of the solution was 2.7. After standing for two hours, the solution was padded onto two samples of 0D sateen. The samples were dried five minutes at C. One sample was exposed to 'NH;, gas for three minutes at 25 C. and then immersed in 10% NH OH for three minutes at 65-70 C. The other sample was exposed to NH gas for five minutes at 25 C. and immersed in 10% NH OH for five minutes at 65-70 C. The samples were washed and dried. The former sample had an add-on of 8.6%, a phosphorus content of 1.82%, and a char length of 3.75 inches; the latter had an add-on of 9.5%, a phosphorus content of 2.24%, and a char length of 3.25 inches.

Example 3 Solution No. 6 (see Example 1) was padded on two samples of OD sateen fabric and the samples dried for five minutes at 85 C. One sample was exposed to NH gas at room temperature for five minutes and then immersed in 10% NH OH for five minutes. The other sample was exposed to NH, gas at room temperature for one minute, and then immersed in 10% NH OH for one minute. The former sample had an add-on of 9.9% and a phosphorus content of 2.19%. The latter sample had an add-on of 10.2% and a phosphorus content of 2.36%. Both samples had good flame resistance. After ten laundering cycles, the phosphorus content was 1.22% and 1.30%, respectively, and the retained flame resistance was moderate.

Example 4 Solutions No. 5 and 6 (see Table I) were allowed to age for seven days and five days, respectively, at room temperature and applied to sateen fabric as described in Example 1. Similar results were obtained.

Example 5 A solution was prepared containing 28.65 parts THPC, 2.38 parts PTA, and 63.00 parts water. Two samples of sateen fabric were padded with the solution. The first sample was dried for five minutes at 85 C., exposed to NH gas for three minutes at room temperature, and then immersed in 29% NH OH for three minutes. The second sample 'was dried for five minutes at C., exposed to NH gas for three minutes at room temperature, and then immersed in 10% NH OH for three minutes. The data before and after ten laundering cycles are shown in Table III.

TABLE III Before laundering After ten laundering cycles Sample Add-on,

'- -No. percent Percent Percent Char length, Percent Percent Char length,

. N P in. N P in.

1 10. 3 1.42 2. 31 3. 6 0. 72 1.27 BEL l 2 5. 3 0. 69 2.13 l. 77

1 BEL means sample burned the entire length.

The flame resistance of both samples was only moderate Example 9 after ten laundering cycles.

' Example 6 Solutions were prepared by dissolving di-methylamidophosphoroxydiamide (DPDA) and THPC in Water as indicated in Table IV TABLE IV Solution Parts of Parts of Parts of Mole ratio of No. THPC DPDA water THPCzDPDA Solution No. 1 formed an opaque gel within three hours. Solution No. 2 began to gel within one hour, but then reliquified within a short time. The other solutions were stable for extended periods of time without gelling.

Solutions 3, 4, and 5 were padded on samples of sateen fabric. The samples were dried for five minutes at 85 C., exposed to NH, gas for five minutes, and then immersed in NH OH for five minutes, and washed. The samples had reduced flammability.

Example 7 A solution was prepared containing 57.3 parts THPC, 7.14 parts PTA, and 130.8 parts water. The pH was 1.6. The solution was padded on two samples of white printcloth. Both samples were dried for five minutes at 85 C., exposed to ammonia gas for three minutes at room temperature and then immersed in 10% ammonium hydroxide for three minutes at room temperature. One of the samples (Sample No. 1) was then washed. The other sample (Sample No. 2) was passed through squeeze rolls to remove excess ammonium hydroxide, cured in an oven for five minutes at 140145 C., and finally washed; Data are shown in Table V before and after ten home laundering cycles.

TABLE VI Before laundering After ten laundering Sample Resin cycles No. add-on Percent Percent Percent Percent P N P N The percent loss of nitrogen and phosphorus after laundering is less for the sample which was cured.

We claim:

1. A process for treating cellulosic material which cornprises:

(a) treating said cellulosic material with an aqueous solution of a further-polymerizable methylol phosphorus polymeric material containing at least one free methylol group attached to a phosphorus atom, said polymeric material prepared by treating a precondensate comprising a partially polymerized mixture of tetrakis(hydroxymethyl)phosphonium chloride and a phosphorus-containing amide from the group consisting of phosphoroxytriamide and dimethylamidophosphoroxydiamide, the mole ratio of said chloride to said amide being about from 0.5 :1 to 6:1 respectively,

(b) drying the treated material,

(0) exposing the treated material to gaseous ammonia for a period of time about from one to five minutes, at a temperature of about from 25 (Ii-100 C.,

TAB LE V R Before laundering After ten laundering cycles esm Sample add-on, Breaking Str. Breaking Str. No. percent (a) (warp) lbs. ((1) (warp), lbs.

1 16. 2 827 41. 1 42. 1 633 39. 8 37. 4 2 15. 6 770 42. 7 39. 8 627 39. 5 35. 6 Control 1, 180 46. 9 660 46. 2

(a) Tearing strength (warp) gms. (b) Bleached.

(c) Bleached and scorched.

(d) Tearing strength (warp) gins. (e) Bleached.

(f) Bleached and scorched.

The strength losses of the treated fabrics after the bleaching and scorching tests are small. The strength retention is good even after ten laundering cycles.

Example 8 A solution was prepared as in Example 7. The solution was then refluxed for thirty minutes and allowed to stand overnight. The acidity of the solution was greater than pH 1. A sample of white printcloth was treated in the same manner as sample 1, in Example 7. The resin add-on was 9.8%, the percent N was 1.16%, the percent P was 2.03%, and the tearing strength was 23.5 lbs. after chlorine bleaching, and 26.8 lbs. after chlorine bleaching and scorching.

7 8 phorus polymeric material containing at least one free 5. The process of claim 4 wherein the phosphorusrconmethylol group attached to a phosphorus atom, said taining amide is phosphoroxytriamide. polymeric material prepared by treating a precon- 6. The process of claim 4 wherein the phosphorus-condensate comprising a partially polymerized mixture of taining amide is dimethylamidophosphoroxydiarnide. tetrakis(hydroxymethyl)phosphonium chloride and a 5 V phosphorus-containing amide selected from the group References Cited consisting of phosphoroxytriamide and dimethyl- UNITED STATES PATENTS amido hos horox diamide, the mole ratio of said chlori e to said ariiide being about from 0.5:1 to 6:1, 2668096 2/1954 Reeves et 117 137 X 2,772,188 11/1956 Reeves et al 117136 respectlvely, and 10 2 98 23 5/ 961 C (b) curing the treated material at a temperature of 1 Oates 117 62'2 X about from {30 to 155 C., for periods of time about WILLIAM D M ARTIN, Primary Examiner. from five minutes to 24 hours, the longer periods of time being applicabl to the lower temperatures. T. R Assistant Examiner- 

